### Please describe the problem.

I did an interactive rebase of the git-annex branch and rolled back the remote git-annex branch. Afterwards `git annex sync` did not merge the remote git-annex branch.

### What steps will reproduce the problem?

```
git init a
cd a
git annex init
git commit -m . --allow-empty

cd ..
git clone a b
cd b
git annex init
git remote rename origin a
cd ../a
git annex fsck
cd ../b
git annex sync

git push a :synced/git-annex
git push -f a 'git-annex^2:git-annex'
git branch -f git-annex 'git-annex^1'
git annex sync
```

After the second sync, `a/git-annex` did not get merged.

### What version of git-annex are you using? On what operating system?

8.20211011 linux

